THE Queen appeared in a black cab outside St Mary’s Hospital in London, where Kate Middleton has just given birth to her third child.

Only it wasn’t really Her Majesty, but a lifelike waxwork mannequin dressed in a pink jacket and pearls.

The crowd of royal fans waiting outside the Paddington hospital found the bizarre prank “very funny”, according to onlookers. The black cab attracted instant attention with many rushing up to the door for a look inside, before having to be told “it’s wax.”

Ladbrokes spokesman Alex Apati said “customers think they’re onto something with Arthur” which has become a punters favourite recently. The agency also favours traditional royal names like Philip, Frederick, and James.

“History and tradition kind of says that the names are very straight down the line ... nothing too out there.

“A gender neutral name? Alex maybe?” he said.

Friends Onkar and Sukhdev Singh said they were “really excited” hearing the news and jumped straight on a train from West London to wait outside the hospital in the hope of catching a glimpse of the young Prince and Princess.

“It’s such an amazing day in history in that it’s the first time a woman has been ahead of a man in succession to the throne,” Onkar said in reference to the fact Charlotte will not be bumped down the line because she is female.

“So that makes a woman fourth in line for the throne after today ... we can all celebrate that as British people.”

Jade, from Bournemouth said “when you actually wake up to the news that she’s gone into labour, it’s just so exciting. The royal family has got so much going on this year as well.”

Friends Barbar and Grace said the birth was “absolutely fantastic” while toasting the baby with a glass of wine.

“As long as it’s healthy and they’re happy then it’s fantastic news,” she said, tipping Albert or Charles for a name.

Vanessa Crossley and Joanne McLoughlin, from Lancashire, told news.com.au how they saw news of the royal arrival while going for a morning run so came back down to watch.

“It’s really exciting ... Nice they’ve got a growing family,” said Joanne, who is picking “traditional English names” for the baby.

“Perfect. It sounds like it’s all gone smoothly,” Vanessa said.

Royalist Terry Hutt, dressed in a suit with the Union Jack flag on it, said: “All I want to see is a healthy baby.” The 82-year-old former soldier slept for a fortnight on the pavement outside the hospital in wait.

Kensington Palace announced the news both online via a noticeboard outside Buckingham Palace, which will stay there for 24 hours.

“Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 1101hrs. The baby weighs 8 lbs 7oz [3.8kg],” the palace said.

“The Duke of Cambridge was present for the birth. The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news.

Speculation is growing over a possible name, with Arthur, Albert, Philip and Frederick among the favourites. Royal names usually have a strong connection with tradition, but despite being born on St George’s Day, the baby is unlikely to be called George, since his eldest brother has taken the name.